1. Field of the Invention
The present invention relates to a reflecting mirror assembly for an autocollimator.
2. Description of the Prior Art
As is well known, a conventional autocollimator is provided with a light source, a reticle plate, a focus plate, and optical system, wherein light from the reticle plate becomes a parallel light beam directed toward a reflecting mirror placed on a test object and is reflected therefrom to the same optical system so as to form an optical image on the focus plate (screen) so that the inclination angle of the reflecting mirror is measured with high accuracy based on the position of the image. Using this principle of the autocollimator it is possible to carry out high-precision measurement of the rotational angle of a rotary disc, the minute deflection of an elastic segment, the perpendicularity of parts and the like. Where the straightness of a test object, e.g. the guide way of a machine bed, is measured, pitching and yawing movements of the test object can be measured by viewing the movements of the image positioned on the screen of the autocollimator while sliding the reflecting mirror rested on the test object, and at this time rolling movement of the test object can be separately measured using a level or a straight-edge and a microindicator, or another autocollimator and a reflecting mirror, whereby the thus measured values of pitching, yawing and rolling of the test object are used to determine the straightness of the test object.
Consequently, so as to be able to measure the straightness of the test object more easily and in a short time, it is desirable to make it possible to measure the rolling movement simultaneously with the pitching and yawing movements using the same screen of the autocollimator.